CAFDRS INNOVATIONS AND FIELD RESULTS

Abstract

The Computer Augmented Field Data Recording System-CAFDRS-is a unique combination of a standard seismic digital field recording system and a mini-computer system, specifically conceived to provide a major advance in monitoring and analysing data as it is being acquired in the field. On-line operations include capability to: composite, vertically stack, correlate VIBROSEIS data, control the recording operation and make power spectrum analysis. Off-line operations include the ability to play back data at a later time, and perform most of these same operations, plus, produce a normal-move-out corrected common-depth-point stacked section. Experience with CAFDRS in the field demonstrates both the versatility of the concept and the effectiveness of being able to analyse data "on the spot" particularly when using the VIBROSEIS technique. Noise, source array and geophone analyses are made "on- line" as the experimental program is conducted. By using the frequency analysis program to obtain power spectra, the optimum vibrator sweep can be established for the particular area.

The 16 bit word base used in the mini-computer system preserves the 76db of dynamic range of the data acquired by the XDS-1010 or the DFS III, two of the standard field systems now used in CAFDRS. The dynamic range of the compositing and correlating operations accomplished with the SPC-16 mini-computers compares favorably with that obtained in a large scale data processing centre.

The noise editing feature included in the double precision floating point compositing program reduces the deteriorating effect that large bursts of random noise have on most composited data. Composited data correlated in the field compares almost exactly with the same data correlated in the data centre. The NMO/CDP raw stacks produced in the field compare favorably with ones produced in the data centre.

Note: VIBROSEIS is a trademark of the Continental Oil Company and DINOSEIS is a trademark of the Atlantic Richfield Oil Company.